A question about your fastboot GUI / fastboot command line: is it suppose to make the kindle switch to fastboot mode? Or do you have to use MfgTool under Windows for that anyway, before one can use the fastboot program?

A question about your fastboot GUI / fastboot command line: is it suppose to make the kindle switch to fastboot mode? Or do you have to use MfgTool under Windows for that anyway, before one can use the fastboot program?

over fastboot by "fastboot.exe setvar bootmode fastboot",
but in this case you would have to have Kindle in fastboot mode.
But you can change the bootmode over ssh too with following commands:

idme -d --bootmode fastboot
sync
reboot

You don't need to flash diags for ssh access, see wiki for way, how to connect over ssh in main mode.

over fastboot by "fastboot.exe setvar bootmode fastboot",
but in this case you would have to have Kindle in fastboot mode.
But you can change the bootmode over ssh too with following commands:

idme -d --bootmode fastboot
sync
reboot

You don't need to flash diags for ssh access, see wiki for way, how to connect over ssh in main mode.

I tried to access with ssh, but connection is refused (over usb0). I feel there is chicken and egg issue: how can I enter fastboot mode without ssh connection, when enabling ssh would require fastboot.

Anyway, I do not want to hijack your thread, so I will discuss these difficulties on another one.